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MPC5674F: clock frequency change

Question asked by Sergey Tarassenko on Aug 29, 2019
Latest reply on Sep 17, 2019 by David Tosenovjan

Hello,

 

I'm little confused regarding clock configuration and LVDCTRIM register. MPC5674F Microcontroller Reference Manual, Rev. 7, 4.6 Initialization says "When the internal regulator is used to generate 1.2V core supply, it is required to write “1100” to the LVDCTRIM field before clock frequency is increased."

 

In my understanding there is always an internal regulator used, either SMPS or LDO, depending on REGSEL connection. So it is always necessary to set LVDCTRIM to 1100 before increasing clock frequency?

I've checked multiple NXP examples for MPC5674F, they all increase clock frequency to 264MHz, however LVDCTRIM is always left on default value 1010 and never changed to recommended 1100 before applying new clock frequency. So is it really required to set LVDCTRIM? What are the possible consequences of not doing so?

 

Thank you in advance!

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